DESTROY THE MOTHER SHIP:

Argon 1 gives you a new mission.

a. The Xenon Mother Ship (M Zero) must be destroyed.

b. Go (S) from Thuruk's Beard, then go (W).

c. We will control the area, you concentrate on the M Zero. Destroy the Laser Towers, then we will help you destroy the ship.

** Argon 1 is there while you work on the towers, but when you're done he doesn't do much.  You might as finish the job yourself. Once M0 is destroyed, contact Argon 1.